The present invention relates to a gas compressor used in a refrigerator or air-conditioner and, more particularly, to a sliding-vane rotary compressor.
FIG. 8 schematically shows the prior art sliding-vane rotary gas compressor in cross section. FIG. 9 is a view taken on line 9—9 of FIG. 8. This gas compressor has a rotor 2 rigidly secured to a rotor shaft 1. When the rotor 2 is driven by a motor (not shown), five vanes 3 slidably held in five slots (not shown), respectively, radially formed in the rotor 2 are rotated in contact with the inner wall of the cylinder chamber 4, thus compressing refrigerant gas.
An intake chamber 6 is formed inside a front head 5. An intake port 7 for drawing in the refrigerant gas to be compressed from an evaporator (not shown) is formed over the intake chamber 6. Two intake holes 8 and 9 are formed in the front head 5 symmetrically about a point to place the intake chamber 6 and the cylinder chamber 4 in communication with each other. Accordingly, the refrigerant gas drawn in from the intake port 7 on the intake chamber 6 flows through the intake chamber 6 and through the intake holes 8, 9, as indicated by the arrow A. Finally, the gas is introduced into the cylinder chamber 4.
Two discharge holes (not shown) corresponding to the intake holes 8 and 9 in the cylinder chamber 4 are formed in a rear-side block 10 on the side of the cylinder chamber 4 and located symmetrically with respect to a point. Discharge valves (not shown) are mounted in the discharge holes, respectively. As shown in FIG. 9, these discharge holes are in communication with openings 11 and 12, respectively, formed in the rear-side block 10 and connected with discharge passages 13 and 14, respectively, formed between the rear-side block 10 and a block 15 for an oil separator. These discharge passages 13 and 14 are connected to each other at 16 close to their ends. At this location 16, the oil separator, indicated by 17, for separating lubricating oil from the refrigerant gas is mounted.
In this prior art sliding-vane rotary gas compressor, when the motor (not shown) rotates the rotor 2 to thereby actuate the vanes 3, the refrigerant gas is drawn into the intake chamber 6 from the intake port 7 as indicated by the arrow A. Then, the gas passes through the intake hole 8 and is drawn into the cylinder chamber 4, where the gas is compressed. The gas is forced out of the opening 12 corresponding to the intake hole 8. Simultaneously with this operation, intake into the intake hole 8 in the cylinder chamber 4 ends. Then, the refrigerant gas is started to be drawn into the cylinder chamber 4 from the intake hole 9, whereby compression is started. When this compression ends, the refrigerant gas is discharged from the opening 11 corresponding to the intake hole 9. Accordingly, the refrigerant gas is discharged from the openings 11 and 12 one after another and intermittently.
The compressed refrigerant gas discharged from the opening 11 or 12 in this way flows through the discharge passage 13 or 14 and is supplied into the oil separator 17, where the lubricating oil is separated from the refrigerant gas. As a result, only the refrigerant gas is expelled to the outside from a discharge port 19 in a discharge chamber 18, as indicated by the arrow B.
Since the gas is discharged from the two openings 11 and 12 in the cylinder chamber 4 intermittently as described above, the pressure is not constant. Rather, higher-order pressure variations are produced according to the rotational frequency of the rotor 2. Because each discharge valve has the five vanes 3 in the two openings 11 and 12, the discharged gas produces five pulsating motions per rotation of the rotor 2.
The two pulsating motions produced in the openings 11 and 12 of the cylinder chamber 4 are shifted in phase by a half wavelength, because the timing at which the gas is discharged from the openings 11 and 12 is designed as described above to smoothen the delivery of the gas. Therefore, the pulsating motions of the refrigerant gas should cancel out until the gas is delivered from the discharge port 19 after flowing through the discharge passage 13, the discharge passage 14, the oil separator 17, and the discharge chamber 18. Hence, discharging pulsating motions due to the fifth-order component of the rotational speed of the compressor should not be transmitted to the outside.
However, the discharge passages 13 and 14 are different in length, as shown in FIG. 9. For this and other reasons, it is impossible to effectively cancel out the discharging pulsating motions described above. As a result, the pulsating motions are transmitted to the outside, producing noise. Use of a silencer may be generally contemplated to solve this problem. However, if such a silencer is used, the whole machine is made bulky. Also, the cost of fabricating the machine is increased greatly, thus presenting a new problem.